Genesis and Consequences of Aberrant DNA Methylation

描述(由申请人提供)：我们的总体研究计划集中在了解DNA甲基化异常的分子基础及其在人类癌症发生中的作用。与启动子区域CpG岛异常甲基化相关的基因沉默是一种常见的表观遗传学改变，导致肿瘤抑制基因和其他基因在人类癌症中失活。目前，关于特定基因如何或为什么屈服于这种异常事件，以及活跃基因进入甲基化和非活跃状态的机制还不太清楚。将DNA甲基化与组蛋白翻译后修饰联系起来的新证据表明，局部染色质结构可能是正常和异常DNA甲基化模式的关键决定因素。我们认为，异常甲基化是由于顺式作用机制的失败，该机制阻止或积极地反对异染色质的扩散。这一更新申请的目标是进一步探索CpG岛在染色质水平上定义一个独特的结构域，以及该结构域的完整性防止正常细胞中异常甲基化的想法。我们的研究将集中在我们实验室发现的一种新基因--TM 1，它在人类乳腺癌和其他癌症中通过表观遗传学手段沉默。具体地说，我们计划确定在未甲基化的CpG岛和甲基化的侧翼DNA之间的边界上发现的DNAsel高灵敏位点是否在顺式基因中起作用，以保护CpG岛免受从头甲基化和周围染色质的影响。其次，我们将表征一种新型的甲基化敏感的复合体，它在未甲基化的状态下与TM 1 CpG岛结合。最后，我们将检验这一假设，即通过维持CpG岛染色质上的等染色标来防止异常甲基化。更好地了解癌症发生过程中DNA甲基化异常的发生和后果的机制，将有助于未来开发旨在防止或逆转沉默过程的新的治疗策略。

DESCRIPTION (provided by applicant): Our overall research initiative is focused on understanding the molecular basis of aberrant DNA methylation and its role in human carcinogenesis. Gene silencing associated with the aberrant methylation of promoter region CpG islands is a common epigenetic alteration that contributes to the inactivation of tumor suppressor and other genes in human cancers. At present, there is little known about how or why particular genes succumb to this aberrant event, and the mechanisms in which an active gene progresses to a methylated and inactive state are not well understood. Emerging evidence linking DNA methylation with posttranslational modification of histones suggests that the local chromatin architecture may be a critical determinant of normal, and abnormal, DNA methylation patterning. We propose that the aberrant methylation arises from a failure in cis of a mechanism that blocks or actively opposes the spread of heterochromatin. The goal of this renewal application is to further explore the idea that CpG islands define a distinct domain at the level of chromatin, and that the integrity of this domain prevents aberrant methylation in normal cells. Our studies will focus on a novel gene identified in our laboratory, TMS1, that is silenced by epigenetic means in human breast and other cancers. Specifically, we plan to determine whether DNAsel hypersentitive sites identified at the boundary between the unmethylated CpG island and methylated flanking DNA act in cis to protect the CpG island from de novo methylation and the influences of surrounding chromatin. Secondly, we will characterize a novel methylation-sensitive complex that binds to the TMS1 CpG island in its unmethylated state. Finally, we will test the hypothesis that aberrant methylation is prevented by the maintenance of a euchromatic mark over CpG island chromatin. A better understanding of the mechanisms underlying the genesis and consequences of aberrant DNA methylation during carcinogenesis will provide for the future development of novel treatment strategies aimed at preventing or reversing the silencing process.